Enphase Energy (ENPH) 10-Q 6 Aug 18 2018 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2018	Jul. 26, 2018
Document and Entity Information [Abstract]
Entity Registrant Name	Enphase Energy, Inc.
Entity Central Index Key	1,463,101
Document Type	10-Q
Document Period End Date	Jun. 30, 2018
Amendment Flag	false
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q2
Current Fiscal Year End	--12-31
Entity Filer Category	Smaller Reporting Company
Entity Common Stock, Shares Outstanding		96,848,549

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 58,471	$ 29,144
Accounts receivable, net of allowances of $3,071 and $2,378 at June 30, 2018 and December 31, 2017, respectively	58,696	65,346
Inventory	17,471	25,999
Prepaid expenses and other assets	20,741	9,957
Total current assets	155,379	130,446
Property and equipment, net	23,100	26,483
Goodwill	3,664	3,664
Intangibles, net	363	515
Other assets	36,030	8,039
Total assets	218,536	169,147
Current liabilities:
Accounts payable	21,895	28,747
Accrued liabilities	31,095	22,447
Deferred revenues, current	34,954	15,691
Warranty obligations, current (includes $3,209 and $2,240 measured at fair value at June 30, 2018 and December 31, 2017, respectively)	8,275	7,427
Debt, current	18,429	17,429
Total current liabilities	114,648	91,741
Long-term liabilities:
Deferred revenues, noncurrent	75,107	29,941
Warranty obligations, noncurrent (includes $9,627 and $7,550 measured at fair value at June 30, 2018 and December 31, 2017, respectively)	23,367	22,389
Other liabilities	1,970	1,880
Debt, noncurrent	33,559	32,322
Total liabilities	248,651	178,273
Commitments and contingencies
Stockholders’ equity:
Preferred stock, $0.00001 par value, 10,000 shares authorized; none issued and outstanding	0	0
Common stock, $0.00001 par value, 150,000,000 shares and 125,000 shares authorized; and 98,082 and 85,914 shares issued and outstanding at June 30, 2018 and December 31, 2017, respectively	1	1
Additional paid-in capital	313,778	287,256
Accumulated deficit	(343,541)	(295,727)
Accumulated other comprehensive loss	(353)	(656)
Total stockholders’ deficit	(30,115)	(9,126)
Total liabilities and stockholders’ equity	$ 218,536	$ 169,147

CONDENSED CONSOLIDATED BALANCE3

CONDENSED CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Allowances, accounts receivable	$ 3,071	$ 2,378
Warranty obligations, current at fair value	3,209	2,240
Warranty obligations, non-current at fair value	$ 9,627	$ 7,550
Preferred stock, par value (in usd per share)	$ 0.00001	$ 0.00001
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in usd per share)	$ 0.00001	$ 0.00001
Common stock, shares authorized (in shares)	150,000,000	125,000,000
Common stock, shares issued (in shares)	98,082,000	85,914,000
Common stock, shares outstanding (in shares)	98,082,000	85,914,000

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Income Statement [Abstract]
Net revenues	$ 75,896	$ 74,704	$ 145,868	$ 129,455
Cost of revenues	53,195	61,157	104,851	108,861
Gross profit	22,701	13,547	41,017	20,594
Operating expenses:
Research and development	9,462	7,947	17,082	17,552
Sales and marketing	6,828	6,274	13,055	12,732
General and administrative	6,969	4,964	13,913	10,797
Restructuring charges	0	3,609	0	10,856
Total operating expenses	23,259	22,794	44,050	51,937
Loss from operations	(558)	(9,247)	(3,033)	(31,343)
Other expense, net:
Interest expense	(2,269)	(2,080)	(4,562)	(4,219)
Other income (expense)	(572)	88	(698)	1,148
Total other expense, net	(2,841)	(1,992)	(5,260)	(3,071)
Loss before income taxes	(3,399)	(11,239)	(8,293)	(34,414)
Provision for income taxes	(339)	(854)	(573)	(984)
Net loss	$ (3,738)	$ (12,093)	$ (8,866)	$ (35,398)
Net loss per share:
Basic and diluted (in usd per share)	$ (0.04)	$ (0.14)	$ (0.09)	$ (0.44)
Shares used in per share calculation:
Basic and diluted (in shares)	97,321	84,434	94,026	80,542

CONDENSED CONSOLIDATED STATEME5

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Net loss	$ (3,738)	$ (12,093)	$ (8,866)	$ (35,398)
Other comprehensive loss:
Foreign currency translation adjustments	15	462	303	123
Comprehensive loss	$ (3,723)	$ (11,631)	$ (8,563)	$ (35,275)

CONDENSED CONSOLIDATED STATEME6

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash flows from operating activities:
Net loss	$ (8,866)	$ (35,398)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	4,469	4,583
Provision for doubtful accounts	753	707
Asset impairment and restructuring	0	1,765
Amortization of debt issuance costs	1,133	1,063
Stock-based compensation	5,860	3,550
Changes in operating assets and liabilities:
Accounts receivable	5,897	3,910
Inventory	8,528	11,121
Prepaid expenses and other assets	(1,551)	(5,338)
Accounts payable, accrued and other liabilities	(3,817)	(14,107)
Warranty obligations	1,826	199
Deferred revenues	(6,791)	3,620
Net cash provided by (used in) operating activities	7,441	(24,325)
Cash flows from investing activities:
Purchases of property and equipment	(1,475)	(3,515)
Net cash used in investing activities	(1,475)	(3,515)
Cash flows from financing activities:
Proceeds from issuance of common stock, net of issuance costs	19,923	26,425
Proceeds from debt	5,580	24,240
Principal payments on term debt	(3,129)	0
Payments under revolving credit facility	0	(10,100)
Proceeds from issuance of common stock under employee stock plans	1,370	170
Net cash provided by financing activities	23,744	40,735
Effect of exchange rate changes on cash	(383)	294
Net increase in cash and cash equivalents	29,327	13,189
Cash and cash equivalents—Beginning of period	29,144	17,764
Cash and cash equivalents—End of period	58,471	30,953
Supplemental disclosures of non-cash investing and financing activities:
Purchases of fixed and intangible assets included in accounts payable	112	311
Warrants issued in connection with debt	$ 0	$ 1,447

DESCRIPTION OF BUSINESS AND BAS

DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION	6 Months Ended
	Jun. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION	DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION Description of Business Enphase Energy, Inc. and subsidiaries (the “Company”) deliver simple, innovative and reliable energy management solutions that advance the worldwide potential of renewable energy. The Company’s semiconductor-based microinverter system converts direct current (DC) electricity to alternating current (AC) electricity at the individual solar module level and brings a system-based, high technology approach to solar energy generation leveraging our design expertise across power electronics, semiconductors, networking, and cloud-based software technologies. Since inception, the Company has shipped over 17 million microinverters, representing over 4 gigawatts of solar photovoltaic (PV) generating capacity, and more than 790,000 Enphase residential and commercial systems have been deployed in over 120 countries. Basis of Presentation and Consolidation The accompanying condensed consolidated financial statements are presented in accordance with accounting principles generally accepted in the U.S, or GAAP. The condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. Unaudited Interim Financial Information These accompanying unaudited condensed consolidated financial statements have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”) for interim financial reporting. In the opinion of management, these unaudited condensed consolidated financial statements reflect all adjustments, consisting of normal recurring items, considered necessary to present fairly the Company's financial condition, results of operations, comprehensive loss and cash flows for the interim periods indicated. The results of operations for the three and six months ended June 30, 2018 are not necessarily indicative of the operating results for the full year. Certain information and footnote disclosures typically included in annual consolidated financial statements have been condensed or omitted. Accordingly, these unaudited interim condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and related notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017 . Other than as discussed in Note 2. “Revenue Recognition” and Note 11. “Stock-based Compensation,” there have been no material changes in the Company’s significant accounting policies during the six months ended June 30, 2018 , as compared to the significant accounting policies described in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017 . Reference is made to the disclosures therein for a summary of the Company’s significant accounting policies. Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of income and expenses during the reporting period. Significant estimates and assumptions reflected in the financial statements include revenue recognition, inventory valuation and accrued warranty obligations. These estimates are based on information available as of the date of the financial statements; therefore, actual results could differ materially from management’s estimates using different assumptions or under different conditions. Recently Adopted Accounting Pronouncements In May 2014, the FASB issued ASU 2014-09, “Revenue from Contracts with Customers,” amending revenue recognition guidance and requiring more detailed disclosures to enable users of financial statements to understand the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. The amended guidance, herein referred to as Topic 606, is effective for annual and interim reporting periods beginning after December 15, 2017, with early adoption permitted for public companies effective for annual and interim reporting periods beginning after December 15, 2016. The Company has adopted Topic 606 effective January 1, 2018, using the modified retrospective transition method. The Company recognized the cumulative effect of applying the new revenue standard as an adjustment to the opening balance of retained earnings on January 1, 2018. The comparative information has not been restated and continues to be reported under the accounting standards in effect for the period presented. See Note 2, “Revenue Recognition,” for additional accounting policy and transition disclosures. In January 2016, the FASB issued ASU 2016-01, “Recognition and Measurement of Financial Assets and Financial Liabilities,” which amends certain aspects of recognition, measurement, presentation, and disclosure of financial instruments. Changes to the current guidance include the accounting for equity investments, the presentation and disclosure requirements for financial instruments, and the assessment of valuation allowance on deferred tax assets related to available-for-sale securities. In addition, ASU 2016-01 establishes an incremental recognition and disclosure requirement related to the presentation of fair value changes of financial liabilities for which the fair value option has been elected. Under this guidance, an entity would be required to separately present in other comprehensive income the portion of the total fair value change attributable to instrument-specific credit risk as opposed to reflecting the entire amount in earnings. ASU 2016-01 is effective for fiscal years and interim periods beginning after December 15, 2017, and upon adoption, an entity should apply the amendments by means of a cumulative-effect adjustment to the balance sheet at the beginning of the first reporting period in which the guidance is effective. Early adoption was not permitted except for the provision to record fair value changes for financial liabilities under the fair value option resulting from instrument-specific credit risk in other comprehensive income. The standard, which was adopted in the first quarter of 2018, did not have a material impact on the condensed consolidated financial statements. In November 2016, the FASB issued Accounting Standards Update No. 2016-18 (ASU 2016-18), “Statement of Cash Flows,” which requires companies to include amounts generally described as restricted cash and restricted cash equivalents in cash and cash equivalents when reconciling beginning-of-period and end-of-period total amounts shown on the statement of cash flows. ASU 2016-18 is effective for fiscal years, and interim periods within those years, beginning after December 15, 2017. The standard, which was adopted in the first quarter of 2018, did not have a material impact on the condensed consolidated financial statements. In May 2017, the FASB issued ASU 2017-09 (ASU 2017-09), "Compensation - Stock Compensation." ASU 2017-09 was issued to provide clarity and reduce both 1) diversity in practice and 2) cost and complexity when applying the guidance in Topic 718 to a change in the terms or conditions of a share-based payment award. ASU 2017-09 provides guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting under Topic 718. ASU 2017-09 is effective for fiscal years, and interim periods within those years, beginning after December 15, 2017. The standard, which was adopted in the first quarter of 2018, did not have a material impact on the condensed consolidated financial statements. Recently Issued Accounting Pronouncements Not Yet Effective In February 2016, the FASB issued Accounting Standards Codification (“ASC”) 842 (“ASC 842”), “Leases,” which replaces the existing guidance in ASC 840, Leases. ASC 842 is effective for fiscal years, and interim periods within those years, beginning after December 15, 2018. ASC 842 requires a dual approach for lessee accounting under which a lessee would account for leases as finance leases or operating leases. Both finance leases and operating leases will result in the lessee recognizing a right-of-use (ROU) asset and a corresponding lease liability. For finance leases the lessee would recognize interest expense and amortization of the ROU asset and for operating leases the lessee would recognize a straight-line total lease expense. The Company is currently evaluating the impact of adoption on the consolidated financial statements.

REVENUE RECOGNISION

REVENUE RECOGNISION	6 Months Ended
	Jun. 30, 2018
Revenue from Contract with Customer [Abstract]
REVENUE RECOGNITION	REVENUE RECOGNITION On January 1, 2018, the Company adopted Topic 606 and applied the modified retrospective method to all contracts that were not completed as of January 1, 2018. Results for reporting periods beginning after January 1, 2018 are presented under Topic 606, while prior period amounts are not adjusted and continue to be reported under the accounting standards in effect in the prior period. The Company recorded a net reduction to opening equity of $38.9 million on January 1, 2018 for the cumulative effect of adopting Topic 606. The impact to net revenues from the adoption of Topic 606 for the six months ended June 30, 2018 was a net increase of $2.5 million . Changes in accounting policies as a result of adopting Topic 606 and nature of goods The most significant impacts upon adoption of Topic 606 were how the Company accounts for revenue related to its Envoy communications device and related Enlighten service and the timing of when certain sales incentives are recognized. Under ASC 605 the Company’s Envoy communications device and Enlighten service were considered two units of accounting, and the portion of the consideration related to the hardware was recognized at the time of sale with the remaining consideration deferred and recognized over the estimated service period. Under ASC 606 the full consideration for these products represents a single performance obligation and is deferred and recognized over the estimated service period. This treatment resulted in a gross increase to deferred revenue of $77.5 million , an increase in deferred costs of $43.4 million and a net increase in accumulated deficit of $34.1 million upon adoption of ASC 606. The Company previously sold its Envoy communications device to certain customers under a long-term financing arrangement. Under ASC 605, this arrangement resulted in the recording of both deferred revenue and unbilled receivables on the balance sheet. The Company’s opening entries related to ASC 606 included the netting of approximately $6.4 million of unbilled receivables against deferred revenue. Thus, the $77.5 million increase to deferred revenue noted above was partially offset by a $6.4 million reclassification of unbilled receivables to deferred revenue. Under ASC 605 the Company recorded certain contra revenue promotions at the later of the date revenue was recognized or the date at which the promotional offer was extended. Under ASC 606 all such contra revenue programs are treated as variable consideration and recognized at the time the related revenue is recorded. This change in timing resulted in an increase in accrued liabilities of approximately $5.6 million and an increase to accumulated deficit of the same amount upon adoption of ASC 606. This change in timing is not expected to have a material impact in subsequent periods. Topic 606 requires upfront contract acquisition costs, such as sales commissions, to be capitalized and amortized over the estimated life of the asset. For contracts that have a duration of less than one year, the Company follows the Topic 606 practical expedient and expense these costs when incurred. Commissions related to the Company’s sale of monitoring hardware and service are capitalized and amortized over the period of the associated revenue, which is 6.5 years . This treatment resulted in an increase in deferred costs of approximately $0.8 million and an increase in accumulated deficit of the same amount upon adoption of ASC 606. Revenues are recognized when control of the promised goods or services are transferred to the Company’s customers in an amount that reflects the consideration that is expected to be received in exchange for those goods or services. The Company generates all of its revenues from contracts with its customers. A description of principal activities from which the Company generates revenues follows. Products Delivered at a Point in Time The Company sells its products to customers in accordance with the terms of the related customer contracts. The Company generates revenues from sales of its microinverter systems, which include microinverter units and related accessories, an Envoy communications gateway and Enlighten service, communications accessories and AC Battery storage solutions to distributors, large installers, OEMs and strategic partners. Microinverter units, microinverter accessories, and AC Battery storage solutions are delivered to customers at a point in time, and in accordance with Topic 606, the Company recognizes revenue for these products when the Company transfers control of the product to the customer, which is generally upon shipment. Products Delivered Over Time The sale of an Envoy communications gateway includes the Company’s Enlighten cloud-based monitoring service. Under Topic 606 the full consideration for these products represents a single performance obligation and is deferred at the sale date and recognized over the estimated service period, which is 6.5 years . The Company also sells certain communication accessories that are delivered over time. The revenue from these products is recognized over the related service period, which is typically 5 or 12 years . Disaggregation of Revenue The Company has one business activity, which is the design, manufacture and sale of microinverter systems for the solar photovoltaic industry. The following table provides information about disaggregated revenue by primary geographical market and timing of revenue recognition for the Company’s single product line (in thousands): Three Months Ended June 30, 2018 Six Months Ended June 30, 2018 Primary geographical markets: United States $ 50,258 $ 93,388 International 25,638 52,480 Total $ 75,896 $ 145,868 Timing of revenue recognition: Products transferred at a point in time $ 65,937 $ 125,308 Products and services transferred over time 9,959 20,560 Total $ 75,896 $ 145,868 Contract Balances As of June 30, 2018 , receivables, contract assets and contract liabilities from contracts with customers consist of the following (in thousands): June 30, 2018 Receivables $ 58,696 Short-term contract assets (Prepaid expenses and other assets) 13,626 Long-term contract assets (Other assets) 33,134 Short-term contract liabilities (Deferred revenues, current) 34,954 Long-term contract liabilities (Deferred revenues, noncurrent) $ 75,107 The Company receives payments from customers based upon contractual billing schedules. Accounts receivable are recorded when the right to consideration becomes unconditional. Contract liabilities are recorded as deferred revenue on the accompanying condensed consolidated balance sheets and include payments received in advance of performance obligations under the contract and are realized when the associated revenue is recognized under the contract. Contract assets include deferred product costs and commissions associated with the deferred revenue and will be amortized along with the associated revenue. The Company had no asset impairment charges related to contract assets in the six months ended June 30, 2018 . Significant changes in the balances of contract liabilities (deferred revenues) and contract assets (prepaid expenses and other assets) during the period are as follows (in thousands): June 30, 2018 Contract Liabilities Balance on January 1, 2018 $ 116,830 Revenue recognized (22,560 ) Increase due to billings 15,791 Balance as of June 30, 2018 $ 110,061 Deferred revenue, current 34,954 Deferred revenue, noncurrent 75,107 Contract Assets Balance on January 1, 2018 $ 47,862 Amount recognized (7,634 ) Increase 6,579 Balance as of June 30, 2018 $ 46,807 Remaining Performance Obligations The following table includes estimated revenue expected to be recognized in future periods related to performance obligations that are unsatisfied or partially unsatisfied at the end of the reporting period (in thousands). June 30, 2018 Remainder of 2018 $ 19,849 2019 29,349 2020 23,194 2021 16,997 2022 11,940 Thereafter 8,732 Total $ 110,061 Practical Expedients and Exemptions The Company generally expenses sales commissions related to products delivered at a point in time when the commissions are incurred because the amortization period would have been less than one year. The Company records these costs as sales and marketing expense. The Company expenses shipping and handling costs as incurred. Impact of Adoption of Topic 606 In accordance with Topic 606, the disclosure of the impact of adoption to the Company’s condensed consolidated statements of operations and condensed consolidated balance sheets was as follows (in thousands): Three Months Ended June 30, 2018 Six Months Ended June 30, 2018 As Reported Adjustments Without Adoption of Topic 606 As Reported Adjustments Without Adoption of Topic 606 Net revenues $ 75,896 $ (2,019 ) $ 73,877 $ 145,868 $ (2,458 ) $ 143,410 Cost of revenues 53,195 (827 ) 52,368 104,851 (996 ) 103,855 Gross profit 22,701 (1,192 ) 21,509 41,017 (1,462 ) 39,555 Operating expenses: Research and development 9,462 — 9,462 17,082 — 17,082 Sales and marketing 6,828 (23 ) 6,805 13,055 (58 ) 12,997 General and administrative 6,969 — 6,969 13,913 — 13,913 Restructuring charges — — — — — — Total operating expenses 23,259 (23 ) 23,236 44,050 (58 ) 43,992 Loss from operations (558 ) (1,169 ) (1,727 ) (3,033 ) (1,404 ) (4,437 ) Other expense, net: Interest expense (2,269 ) — (2,269 ) (4,562 ) — (4,562 ) Other income (expense) (572 ) — (572 ) (698 ) — (698 ) Total other expense, net (2,841 ) — (2,841 ) (5,260 ) — (5,260 ) Loss before income taxes (3,399 ) (1,169 ) (4,568 ) (8,293 ) (1,404 ) (9,697 ) Provision for income taxes (339 ) — (339 ) (573 ) — (573 ) Net loss $ (3,738 ) $ (1,169 ) $ (4,907 ) $ (8,866 ) $ (1,404 ) $ (10,270 ) Net loss per share: Basic and diluted $ (0.04 ) $ (0.01 ) $ (0.05 ) $ (0.09 ) $ (0.02 ) $ (0.11 ) Shares used in per share calculation: Basic and diluted 97,321 97,321 94,026 94,026 June 30, 2018 As Reported Adjustments Without Adoption of Topic 606 Prepaid expenses and other $ 20,741 $ (9,878 ) $ 10,863 Other assets 36,030 (27,856 ) 8,174 Accrued liabilities 31,095 (5,180 ) 25,915 Deferred revenues 34,954 (19,884 ) 15,070 Deferred revenues, noncurrent 75,107 (50,210 ) 24,897 Accumulated deficit $ (343,541 ) $ 37,540 $ (306,001 )

INVENTORY

INVENTORY	6 Months Ended
	Jun. 30, 2018
Inventory Disclosure [Abstract]
INVENTORY	INVENTORY Inventory as of June 30, 2018 and December 31, 2017 consists of the following (in thousands): June 30, December 31, Raw materials $ 2,889 $ 2,341 Finished goods 14,582 23,658 Total inventory $ 17,471 $ 25,999

WARRANTY OBLIGATIONS

WARRANTY OBLIGATIONS	6 Months Ended
	Jun. 30, 2018
Product Warranties Disclosures [Abstract]
WARRANTY OBLIGATIONS	WARRANTY OBLIGATIONS The Company’s warranty activities during the three and six months ended June 30, 2018 and 2017 were as follows (in thousands): Three Months Ended Six Months Ended 2018 2017 2018 2017 Warranty obligations, beginning of period $ 30,625 $ 31,995 $ 29,816 $ 31,414 Accruals for warranties issued during period 775 1,089 1,533 1,921 Changes in estimates 1,378 (91 ) 2,828 203 Settlements (2,099 ) (1,981 ) (3,775 ) (3,598 ) Increase due to accretion expense 520 499 939 993 Other 443 102 301 680 Warranty obligations, end of period $ 31,642 $ 31,613 $ 31,642 $ 31,613 Less current portion $ (8,275 ) $ (8,032 ) Noncurrent $ 23,367 $ 23,581 As of June 30, 2018 , the $31.6 million of warranty obligations included $12.8 million measured at fair value. See Note 5, “Fair Value Measurements” for additional information.

FAIR VALUE MEASUREMENTS

FAIR VALUE MEASUREMENTS	6 Months Ended
	Jun. 30, 2018
Fair Value Disclosures [Abstract]
FAIR VALUE MEASUREMENTS	FAIR VALUE MEASUREMENTS The accounting guidance defines fair value as the price that would be received from selling an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. When determining the fair value measurements for assets and liabilities recorded at fair value, the Company considers the principal or most advantageous market in which it would transact and considers assumptions that market participants would use when pricing the asset or liability, such as inherent risk, transfer restrictions, and risk of nonperformance. The fair value hierarchy requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. An asset’s or liability’s categorization within the fair value hierarchy is based upon the lowest level of input that is significant to the fair value measurement. Three levels of inputs may be used to measure fair value: • Level 1—Valuations based on quoted prices in active markets for identical assets or liabilities that the Company is able to access. Since valuations are based on quoted prices that are readily and regularly available in an active market, valuation of such assets or liabilities do not entail a significant degree of judgment. • Level 2—Valuations based on one or more quoted prices in markets that are not active or for which all significant inputs are observable, either directly or indirectly. • Level 3—Valuations based on inputs that are unobservable and significant to the overall fair value measurement. The following table presents the Company’s liabilities that were measured at fair value on a recurring basis and its categorization within the fair value hierarchy at June 30, 2018 and December 31, 2017 (in thousands): Fair Value June 30, December 31, Liabilities: Warranty obligations Level 3 $ 12,836 $ 9,790 Third party option to purchase receivables at a discount Level 3 — 700 Fair Value Option for Warranty Obligations Related to Microinverters Sold Since January 1, 2014 The Company’s warranty obligations related to microinverters sold since January 1, 2014 provide the Company the right, but not the requirement, to assign its warranty obligations to a third-party. Under Accounting Standards Codification (“ASC”) 825—Financial Instruments, (“fair value option”), an entity may choose to elect the fair value option for such warranties at the time it first recognizes the eligible item. The Company made an irrevocable election to account for all eligible warranty obligations associated with microinverters sold since January 1, 2014 at fair value. This election was made to reflect the underlying economics of the time value of money for an obligation that will be settled over an extended period of up to 25 years. The Company estimates the fair value of warranty obligations by calculating the warranty obligations in the same manner as for sales prior to January 1, 2014 and applying an expected present value technique to that result. The expected present value technique, an income approach, converts future amounts into a single current discounted amount. In addition to the key estimates of failure rates, claim rates and replacement costs, the Company used certain Level 3 inputs which are unobservable and significant to the overall fair value measurement. Such additional assumptions included a discount rate based on the Company’s credit-adjusted risk-free rate and compensation comprised of a profit element and risk premium required of a market participant to assume the obligation. The following table provides information regarding changes in nonfinancial liabilities related to the Company’s warranty obligations measured at fair value on a recurring basis using significant unobservable inputs (Level 3) for the periods indicated (in thousands): Three Months Ended Six Months Ended 2018 2017 2018 2017 Balance at beginning of period $ 11,719 $ 11,627 $ 9,790 $ 10,332 Accruals for warranties issued during period 775 1,080 1,533 1,910 Changes in estimates 210 (351 ) 1,995 (617 ) Settlements (831 ) (393 ) (1,722 ) (735 ) Increase due to accretion expense 520 499 939 994 Other 443 102 301 680 Balance at end of period $ 12,836 $ 12,564 $ 12,836 $ 12,564 Quantitative and Qualitative Information about Level 3 Fair Value Measurements As of June 30, 2018 , the significant unobservable inputs used in the fair value measurement of the Company’s liabilities designated as Level 3 are as follows: Item Measured at Fair Value Valuation Technique Description of Significant Unobservable Input Percent Used (Weighted-Average) Warranty obligations for microinverters sold since January 1, 2014 Discounted cash flows Profit element and risk premium 16% Credit-adjusted risk-free rate 16% As of December 31, 2017 , the significant unobservable inputs used in the fair value measurement of the Company’s liabilities designated as Level 3 are as follows: Item Measured at Fair Value Valuation Technique Description of Significant Unobservable Input Percent Used (Weighted-Average) Warranty obligations for microinverters sold since January 1, 2014 Discounted cash flows Profit element and risk premium 17% Credit-adjusted risk-free rate 17% Third party option to purchase receivables at a discount Discounted cash flows Counter party credit-adjusted risk-free rate 4% Sensitivity of Level 3 Inputs Warranty Obligations Each of the significant unobservable inputs is independent of the other. The profit element and risk premium are estimated based on requirements of a third-party participant willing to assume the Company’s warranty obligations. The credit-adjusted risk free rate (“discount rate”) is determined by reference to the Company’s own credit standing at the fair value measurement date. Increasing or decreasing the profit element and risk premium input by 100 basis points would have a nominal impact on the fair value measurement of the liability. Increasing the discount rate by 100 basis points would result in a $0.6 million reduction of the liability. Decreasing the discount rate by 100 basis points would result in a $0.6 million increase to the liability.

GOODWILL AND INTANGIBLE ASSETS

GOODWILL AND INTANGIBLE ASSETS	6 Months Ended
	Jun. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
GOODWILL AND INTANGIBLE ASSETS	GOODWILL AND INTANGIBLE ASSETS The following table presents the details of the Company’s goodwill and purchased intangible assets as of June 30, 2018 and December 31, 2017 (in thousands): June 30, 2018 December 31, 2017 Gross Accumulated Amortization Net Gross Accumulated Amortization Net Goodwill $ 3,664 $ — $ 3,664 $ 3,664 $ — $ 3,664 Other indefinite-lived intangibles $ 286 $ — $ 286 $ 286 $ — $ 286 Intangible assets with finite lives: Patents and licensed technology 1,665 (1,588 ) 77 1,665 (1,436 ) 229 Total purchased intangible assets $ 1,951 $ (1,588 ) $ 363 $ 1,951 $ (1,436 ) $ 515 In July 2014, the Company purchased certain patents related to system interconnection and photovoltaic AC module construction. The patents were amortized over their legal life of 3 years . In October 2015, the Company licensed certain technology related to ASIC development for a 3 year term, which is also its estimated useful life. For the six months ended June 30, 2018 , amortization expense related to intangible assets was $0.1 million . The remaining $0.1 million of patents and licensed technology will be amortized during the remainder of 2018.

RESTRUCTURING

RESTRUCTURING	6 Months Ended
	Jun. 30, 2018
Restructuring and Related Activities [Abstract]
RESTRUCTURING	RESTRUCTURING In the third quarter of 2016, the Company began implementing restructuring actions to lower its operating expenses. The restructuring actions have included reductions in the Company’s global workforce, the elimination of certain non-core projects, consolidation of office space at the Company’s corporate headquarters and the engagement of management consultants to assist the Company in making organizational and structural changes to improve operational efficiencies and reduce expenses. The Company substantially completed its restructuring activities in 2017. The following table presents the details of the Company’s restructuring charges for the periods indicated (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 Employee severance and benefit arrangements $ — $ 123 $ — $ 1,715 Asset impairments — — — 522 Consultants engaged in restructuring activities — 3,000 — 7,000 Lease loss reserves and contract termination costs — 486 — 1,619 Total restructuring and asset impairment charges $ — $ 3,609 $ — $ 10,856 The following table provides information regarding changes in the Company’s accrued restructuring balance for the periods indicated (in thousands): Employee Severance and Benefits Lease Loss Reserves and Contractual Obligations Total Balance at end of period as of December 31, 2017 $ 229 $ 1,094 $ 1,323 Cash payments and receipts, net (229 ) 54 (175 ) Balance at end of period as of June 30, 2018 $ 0 $ 1,148 $ 1,148

DEBT

DEBT	6 Months Ended
	Jun. 30, 2018
Debt Disclosure [Abstract]
DEBT	DEBT Term Loan In July 2016, the Company entered into a Loan and Security Agreement (the “Original Term Loan Agreement”) with lenders that are affiliates of Tennenbaum Capital Partners, LLC (the “Lenders” or “TCP”). Under the agreement, the Lenders committed to advance a term loan in an aggregate principal amount of up to $25.0 million with a maturity date of July 1, 2020. The Company borrowed the entire $25.0 million of term loan commitments on the loan closing date. Monthly payments due through June 30, 2017 were interest only, followed by consecutive equal monthly payments of principal plus accrued interest that were to begin on July 1, 2017 and continue through the maturity date. The term loan provided for an interest rate per annum equal to the higher of (i) 10.25% or (ii) LIBOR plus 9.5625% , subject to a 1.0% reduction if the Company achieves minimum levels of Revenue and EBITDA (each as defined in the Original Term Loan Agreement) for the twelve-consecutive month period ending June 30, 2017 as set forth in the Original Term Loan Agreement. In addition, the Company paid a commitment fee of 3.3% of the loan amount upon closing and a closing fee of 10.0% of the loan amount is payable in four equal installments at each anniversary of the closing date. The Company could elect to prepay the loan by incurring a prepayment fee between 1% and 3% of the principal amount of the term loan depending on the timing and circumstances of prepayment. In February 2017, the Company entered into an Amended and Restated Loan and Security Agreement (the “Loan Agreement”) that amended and restated the Original Term Loan Agreement. The Loan Agreement provides for a $25.0 million secured term loan to the Company (the “New Term Loan”), which is in addition to the $25.0 million secured term loan borrowed by the Company under the Original Term Loan Agreement (together with the “New Term Loan” the “Term Loans”). The New Term Loan has the same July 1, 2020 maturity date that was applicable to the Original Term Loan Agreement. The New Term Loan was fully drawn at closing, with approximately $10.3 million of the proceeds used to repay existing combined principal and interest due under the Company’s Revolver with Wells Fargo. Upon the repayment of loans under the Wells Fargo Revolver, the Wells Fargo Revolving Credit Agreement was terminated. The Company used the remainder of the proceeds from the New Term Loan for general corporate purposes. Monthly payments under the Term Loans through February 28, 2018 are interest only, followed by consecutive equal monthly payments of principal plus accrued interest beginning on March 1, 2018 and continuing through the maturity date. Interest on the Term Loans is the greater of (a) 10.3125% , and (b) a fluctuating rate of interest per annum equal to the three-month LIBOR Rate (rounded up to the nearest 1/16th of one percent) plus 9.25% . In addition, the Company paid a commitment fee of 3.0% of the New Term Loan amount upon closing and a closing fee of 4.0% of the New Term Loan amount, which is payable with the closing fee under the Original Term Loan Agreement in four equal installments at each anniversary of the closing date of the Original Term Loan Agreement. The Company may elect to prepay the Term Loans by incurring a prepayment fee between 1% and 3% of the principal amount of the Term Loans depending on the timing and circumstances of prepayment. On February 28, 2018, the Company entered into a Second Amendment to the Term Loans. The Second Amendment decreased by 50% the amount of principal repayments required under the Loan Agreement for the period from March 1, 2018 through December 31, 2018 and provided that the Company shall not prepay any part of the Term Loans during that same period without the Collateral Agent’s prior written consent. The Term Loans are secured by a first-priority security interest on substantially all assets of the Company; provided, however, that the security interest in the Company’s intellectual property may be released if the Company satisfies certain requirements. The Company’s obligations under the Term Loans are not guaranteed by any of the Company’s existing subsidiaries, nor have any existing subsidiaries of the Company pledged any of their assets to secure the Term Loans. The Loan Agreement requires that (i) at all times from the closing date to and including March 31, 2018, the Company, and any future guarantors, have Unrestricted Cash (as defined in the Loan Agreement) of at least $10.0 million ; (ii) at all times from the closing date to and including March 31, 2018, that the aggregate amount of Consolidated Unrestricted Cash, plus the value of Consolidated Receivables, plus the value of Consolidated Inventory (each as defined in the Loan Agreement) divided by the outstanding principal amount of Term Loans, shall equal or exceed 1.5 ; and (iii) at all times from April 1, 2018 and thereafter, that the aggregate amount of Consolidated Unrestricted Cash, plus the value of Consolidated Receivables, plus the value of Consolidated Inventory divided by the outstanding principal amount of Term Loans, shall equal or exceed 1.75 . In addition, the Loan Agreement is subject to customary affirmative and negative covenants including restrictions on creation of liens, dispositions of assets, mergers, changing the nature of its business and dividends and other distributions, in each case subject to certain exceptions. The Loan Agreement also contains certain customary events of default including, but not limited to, failure to pay interest, principal and fees or other amounts when due, material breach of any representation or warranty, covenant defaults, cross defaults to other material indebtedness, events of bankruptcy and the occurrence of a material adverse change (as defined in the agreement) to the Company’s business. The Term Loan Agreement offers TCP customary rights and remedies in any event of default, including the ability to declare all amounts outstanding immediately due and payable. In connection with the New Term Loan, the Company issued to the Lenders warrants to purchase an aggregate 1,220,000 shares of the Company’s Common Stock at an exercise price of $1.05 per share. The warrants have a term of seven years and contain a “cashless exercise” feature that allows the holder to exercise the warrant without a cash payment upon the terms set forth therein. The Company estimated the fair value of the warrants by using the Black-Scholes approach and the following assumptions: stock price of $1.56 ; strike price of $1.05 ; volatility of 85.9% , risk-free rate of 2.23% ; dividend yield of 0% ; and a 7 year term. The resulting fair value was used to allocate the proceeds from the Term Loan between liability and equity components. The Company classified the warrants as equity and allocated the proceeds from the Term Loan and warrants using the relative fair value method. Using this method, the Company allocated $1.4 million to the warrants, which was recorded as equity. This amount represents debt discount that will be amortized to interest expense over the term of the loan. The Lenders converted the warrants into 912,067 shares of the Company’s common stock in a cashless exercise in the first quarter of 2018. As of June 30, 2018 , the estimated schedule of principal payments due on the term loan is as follows (in thousands): Year Amounts 2018 $ 4,779 2019 25,238 2020 16,854 Total $ 46,871 Sale of Long Term Financing Receivables The Company entered into an agreement with a third party in the fourth quarter of 2017 to sell certain current and future receivables at a discount. In December 2017, the third party made an initial purchase of receivables that resulted in net proceeds to the Company of $2.8 million . This transaction was recorded as debt on the accompanying consolidated balance sheets, and the debt balance will be relieved by January 2019 as the underlying receivables are settled. During the six months ended June 30, 2018 , the third party made three additional purchases of receivables that resulted in total net proceeds to the Company of $5.6 million . These transactions were recorded as debt on the accompanying consolidated balance sheets, and the total associated debt balance will be relieved by September 2021 as the underlying receivables are settled. After the initial purchase, the buyer had the option to purchase certain additional future receivables at various fixed discounts. This option was valued at $0.7 million and was recorded as a liability with a corresponding offset to debt as of December 31, 2017. As of June 30, 2018 , all purchases relating to this option had been made, and the liability has been relieved. See Note 5, “Fair Value Measurements” for additional information. Long-term debt was comprised of the following at June 30, 2018 and December 31, 2017 (in thousands): June 30, December 31, Term loan $ 46,871 $ 50,000 Less unamortized discount and issuance costs (1,557 ) (2,111 ) Carrying amount of term loan 45,314 47,889 Sale of long term financing receivable recorded as debt 6,674 2,562 Less value of future purchase option — (700 ) Carrying amount of sale of long term financing receivable recorded as debt 6,674 1,862 Total carrying amount of debt 51,988 49,751 Less current portion term loan (16,380 ) (15,715 ) Less current portion of long term financing receivable recorded as debt (2,049 ) (1,714 ) Long-term debt $ 33,559 $ 32,322 Revolving Credit Facility The Company had a $50.0 million revolving credit facility with Wells Fargo Bank, N.A. (“Wells Fargo”) that was entered into in November 2012. The Revolver had a balance of $10.1 million as of December 31, 2016 and was fully repaid and terminated in February 2017.

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	6 Months Ended
	Jun. 30, 2018
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES From time to time, the Company may be involved in litigation relating to claims arising out of its operations. The Company is not currently involved in any material legal proceedings. The Company may, however, be involved in material legal proceedings in the future. Such matters are subject to uncertainty and there can be no assurance that such legal proceedings will not have a material adverse effect on its business, results of operations, financial position or cash flows. The Company was previously involved in a dispute with a supplier regarding purchase volume commitments for which the Company recorded a liability of $1.8 million in the first quarter of 2018. The matter was resolved in the second quarter of 2018 for approximately $1.8 million . On June 12, 2018, the Company entered into an Asset Purchase Agreement (“APA”) with SunPower Corporation (“SunPower”) to purchase assets primarily relating to SunPower’s microinverter business (the “Business”). Upon the closing of the APA, which is currently expected to occur in the third quarter of 2018 (“Closing”), Enphase will acquire intellectual property, technology and other assets primarily relating to the Business and will assume certain contracts and other liabilities of the Business for the following consideration: (i) $15,000,000 payable in cash at Closing; (ii) 7,500,000 shares of Enphase common stock issuable to SunPower at Closing; and (iii) an additional cash payment of $10,000,000 payable by Enphase to SunPower on the earlier of the four month anniversary of the Closing and December 28, 2018.

SALE OF COMMON STOCK

SALE OF COMMON STOCK	6 Months Ended
	Jun. 30, 2018
Equity [Abstract]
SALE OF COMMON STOCK	SALE OF COMMON STOCK On February 4, 2018, the Company entered into a Securities Purchase Agreement with an investor pursuant to which the Company, in a private placement, issued and sold to the investor 9,523,809 shares of the Company’s common stock at a price per share of $2.10 , for gross proceeds of $20.0 million .

STOCK-BASED COMPENSATION

STOCK-BASED COMPENSATION	6 Months Ended
	Jun. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
STOCK-BASED COMPENSATION	STOCK-BASED COMPENSATION The Company has adopted certain equity incentive and stock purchase plans as described in the consolidated financial statements and related notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017 . Equity Awards Activity Stock Options The following is a summary of stock option activity for the six months ended June 30, 2018 (in thousands, except per share data): Number of Shares Outstanding Weighted- Average Exercise Price per Share Outstanding at December 31, 2017 8,426 $ 1.77 Granted 213 4.43 Exercised (803 ) 1.73 Canceled (149 ) 5.06 Outstanding at June 30, 2018 7,687 $ 1.78 The intrinsic value of options exercised in the six months ended June 30, 2018 was $3.0 million . As of June 30, 2018 , the intrinsic value of options outstanding was $38.6 million based on the closing price of the Company’s stock as of June 30, 2018 . Restricted Stock Units and Performance Stock Units The following is a summary of restricted stock unit (“RSU”) and performance stock unit (“PSU”) activity for the six months ended June 30, 2018 (in thousands, except per share data): RSUs and PSUs Weighted Average Outstanding at December 31, 2017 3,505 $ 2.03 Granted 3,536 3.47 Vested (702 ) 2.52 Canceled (250 ) 2.19 Outstanding at June 30, 2018 6,089 $ 2.80 The total intrinsic value of RSUs and PSUs that vested in the six months ended June 30, 2018 was $3.0 million . As of June 30, 2018 , the intrinsic value of RSUs and PSUs outstanding was $41.0 million based on the closing price of the Company’s stock as of June 30, 2018 . Stock-based compensation expense is measured at the grant date based on the fair value of the award. During the second quarter of 2018 the Company issued a PSU grant of 1.4 million shares, 720,000 of which include market conditions. Each grantee is granted a target award of PSUs and may earn between 0% and 150% of the target award depending on the Company’s performance against the performance goals. For PSUs, the grant date fair value is recognized as expense when the performance condition is probable of being achieved, and then on a graded basis over the requisite service period. The fair value of awards containing market conditions was determined using a Monte Carlo simulation model based upon the terms of the conditions, the expected volatility of the underlying security, and other relevant factors. The weighted average estimated fair value of the PSUs without market conditions was $4.57 per share, and the weighted average estimated fair value of the PSUs with market conditions was $4.54 per share. On April 3, 2017, the Company commenced a Tender Offer (the “Offer”) to exchange out of the money stock options for restricted stock units. The Offer expired on Monday, May 1, 2017. Pursuant to the Offer, the Company accepted elections to exchange options to purchase 2,362,470 shares of common stock and issued replacement awards of RSUs for 733,559 shares of common stock. As the transaction approximated a value-for-value exchange, it did not have a material impact on the Company’s stock-based compensation expense. Stock-Based Compensation Expense Compensation expense for all stock-based awards expected to vest is measured at fair value on the date of grant and recognized ratably over the requisite service period. The following table summarizes the components of total stock-based compensation expense included in the condensed consolidated statements of operations for the periods presented (in thousands): Three Months Ended Six Months Ended 2018 2017 2018 2017 Cost of revenues $ 417 $ 211 $ 615 $ 449 Research and development 1,149 636 1,767 1,387 Sales and marketing 997 285 1,358 663 General and administrative 1,725 489 2,120 1,051 Total $ 4,288 $ 1,621 $ 5,860 $ 3,550 The following table summarizes the various types of stock-based compensation expense for the periods presented (in thousands): Three Months Ended Six Months Ended 2018 2017 2018 2017 Stock options and RSUs and PSUs $ 3,975 $ 1,291 $ 5,293 $ 2,890 Employee stock purchase plan 313 330 567 660 Total $ 4,288 $ 1,621 $ 5,860 $ 3,550 The following table presents the weighted-average grant date fair value of options granted for the periods presented and the assumptions used to estimate those values using a Black-Scholes option pricing model: Three Months Ended Six Months Ended 2018 2017 2018 2017 Weighted average grant date fair value $ 3.51 $ 0.71 $ 2.74 $ 0.71 Expected term (in years) 3.8 4.6 4.0 4.6 Expected volatility 89.7 % 84.9 % 88.1 % 85.0 % Annual risk-free rate of return 2.7 % 1.8 % 2.6 % 1.8 % Dividend yield 0.0 % 0.0 % 0.0 % 0.0 % As of June 30, 2018 , there was approximately $16.8 million of total unrecognized compensation expense related to unvested equity awards expected to be recognized over a weighted-average period of 2.7 years.

INCOME TAXES

INCOME TAXES	6 Months Ended
	Jun. 30, 2018
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES The Company used the discrete tax approach in calculating the tax expense for the three and six months ended June 30, 2018 and 2017 due to the fact that a relatively small change in the Company’s projected pre-tax net income (loss) could result in a volatile effective tax rate. Under the discrete method, the Company determines its tax (expense) benefit based upon actual results as if the interim period was an annual period. The tax provision recorded was primarily related to income taxes attributable to its foreign operations.

NET LOSS PER SHARE

NET LOSS PER SHARE	6 Months Ended
	Jun. 30, 2018
Earnings Per Share [Abstract]
NET LOSS PER SHARE	NET LOSS PER SHARE Basic net loss per share is computed by dividing net loss by the weighted average number of shares of common stock outstanding during the period. Diluted loss per share is computed in a similar manner, but it also includes the effect of potential common shares outstanding during the period, when dilutive. Potential common shares include outstanding in-the-money stock options, restricted stock units, shares to be purchased under the Company’s employee stock purchase plan and warrants to purchase common stock. The dilutive effect of potentially dilutive common shares is reflected in diluted earnings per share by application of the treasury stock method. To the extent these potential common shares are antidilutive, they are excluded from the calculation of diluted net loss per share. The following table presents the computation of basic and diluted net loss per share for the periods presented (in thousands, except per share data): Three Months Ended Six Months Ended 2018 2017 2018 2017 Numerator: Net loss $ (3,738 ) $ (12,093 ) $ (8,866 ) $ (35,398 ) Denominator: Weighted average common shares outstanding 97,321 84,434 94,026 80,542 Net loss per share, basic and diluted $ (0.04 ) $ (0.14 ) $ (0.09 ) $ (0.44 ) As the Company incurred a net loss for all periods presented, potential dilutive securities from employee stock options, restricted stock units and warrants have been excluded from the diluted net loss per share computations because the effect of including such shares would have been anti-dilutive. The following table sets forth the potentially dilutive securities excluded from the computation of the diluted net loss per share (in thousands): Three Months Ended Six Months Ended 2018 2017 2018 2017 Employee stock options 8,102 8,068 8,259 8,262 RSUs and PSUs 5,710 2,017 4,690 1,276 Warrants to purchase common stock — 1,220 — 944 Total 13,812 11,305 12,949 10,482

DESCRIPTION OF BUSINESS AND B20

DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION (Policies)	6 Months Ended
	Jun. 30, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation and Consolidation	Basis of Presentation and Consolidation The accompanying condensed consolidated financial statements are presented in accordance with accounting principles generally accepted in the U.S, or GAAP. The condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.
Unaudited Interim Financial Information	Unaudited Interim Financial Information These accompanying unaudited condensed consolidated financial statements have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”) for interim financial reporting. In the opinion of management, these unaudited condensed consolidated financial statements reflect all adjustments, consisting of normal recurring items, considered necessary to present fairly the Company's financial condition, results of operations, comprehensive loss and cash flows for the interim periods indicated. The results of operations for the three and six months ended June 30, 2018 are not necessarily indicative of the operating results for the full year. Certain information and footnote disclosures typically included in annual consolidated financial statements have been condensed or omitted. Accordingly, these unaudited interim condensed consolidated financial statements should be read in conjunction with the consolidated financial statements and related notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017 .
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of income and expenses during the reporting period. Significant estimates and assumptions reflected in the financial statements include revenue recognition, inventory valuation and accrued warranty obligations. These estimates are based on information available as of the date of the financial statements; therefore, actual results could differ materially from management’s estimates using different assumptions or under different conditions.
Recently Adopted Accounting Pronouncements and Recently Issued Accounting Pronouncements Not Yet Effective	Recently Adopted Accounting Pronouncements In May 2014, the FASB issued ASU 2014-09, “Revenue from Contracts with Customers,” amending revenue recognition guidance and requiring more detailed disclosures to enable users of financial statements to understand the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers. The amended guidance, herein referred to as Topic 606, is effective for annual and interim reporting periods beginning after December 15, 2017, with early adoption permitted for public companies effective for annual and interim reporting periods beginning after December 15, 2016. The Company has adopted Topic 606 effective January 1, 2018, using the modified retrospective transition method. The Company recognized the cumulative effect of applying the new revenue standard as an adjustment to the opening balance of retained earnings on January 1, 2018. The comparative information has not been restated and continues to be reported under the accounting standards in effect for the period presented. See Note 2, “Revenue Recognition,” for additional accounting policy and transition disclosures. In January 2016, the FASB issued ASU 2016-01, “Recognition and Measurement of Financial Assets and Financial Liabilities,” which amends certain aspects of recognition, measurement, presentation, and disclosure of financial instruments. Changes to the current guidance include the accounting for equity investments, the presentation and disclosure requirements for financial instruments, and the assessment of valuation allowance on deferred tax assets related to available-for-sale securities. In addition, ASU 2016-01 establishes an incremental recognition and disclosure requirement related to the presentation of fair value changes of financial liabilities for which the fair value option has been elected. Under this guidance, an entity would be required to separately present in other comprehensive income the portion of the total fair value change attributable to instrument-specific credit risk as opposed to reflecting the entire amount in earnings. ASU 2016-01 is effective for fiscal years and interim periods beginning after December 15, 2017, and upon adoption, an entity should apply the amendments by means of a cumulative-effect adjustment to the balance sheet at the beginning of the first reporting period in which the guidance is effective. Early adoption was not permitted except for the provision to record fair value changes for financial liabilities under the fair value option resulting from instrument-specific credit risk in other comprehensive income. The standard, which was adopted in the first quarter of 2018, did not have a material impact on the condensed consolidated financial statements. In November 2016, the FASB issued Accounting Standards Update No. 2016-18 (ASU 2016-18), “Statement of Cash Flows,” which requires companies to include amounts generally described as restricted cash and restricted cash equivalents in cash and cash equivalents when reconciling beginning-of-period and end-of-period total amounts shown on the statement of cash flows. ASU 2016-18 is effective for fiscal years, and interim periods within those years, beginning after December 15, 2017. The standard, which was adopted in the first quarter of 2018, did not have a material impact on the condensed consolidated financial statements. In May 2017, the FASB issued ASU 2017-09 (ASU 2017-09), "Compensation - Stock Compensation." ASU 2017-09 was issued to provide clarity and reduce both 1) diversity in practice and 2) cost and complexity when applying the guidance in Topic 718 to a change in the terms or conditions of a share-based payment award. ASU 2017-09 provides guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting under Topic 718. ASU 2017-09 is effective for fiscal years, and interim periods within those years, beginning after December 15, 2017. The standard, which was adopted in the first quarter of 2018, did not have a material impact on the condensed consolidated financial statements. Recently Issued Accounting Pronouncements Not Yet Effective In February 2016, the FASB issued Accounting Standards Codification (“ASC”) 842 (“ASC 842”), “Leases,” which replaces the existing guidance in ASC 840, Leases. ASC 842 is effective for fiscal years, and interim periods within those years, beginning after December 15, 2018. ASC 842 requires a dual approach for lessee accounting under which a lessee would account for leases as finance leases or operating leases. Both finance leases and operating leases will result in the lessee recognizing a right-of-use (ROU) asset and a corresponding lease liability. For finance leases the lessee would recognize interest expense and amortization of the ROU asset and for operating leases the lessee would recognize a straight-line total lease expense. The Company is currently evaluating the impact of adoption on the consolidated financial statements.
Fair Value Measurements	The accounting guidance defines fair value as the price that would be received from selling an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date. When determining the fair value measurements for assets and liabilities recorded at fair value, the Company considers the principal or most advantageous market in which it would transact and considers assumptions that market participants would use when pricing the asset or liability, such as inherent risk, transfer restrictions, and risk of nonperformance. The fair value hierarchy requires an entity to maximize the use of observable inputs and minimize the use of unobservable inputs when measuring fair value. An asset’s or liability’s categorization within the fair value hierarchy is based upon the lowest level of input that is significant to the fair value measurement. Three levels of inputs may be used to measure fair value: • Level 1—Valuations based on quoted prices in active markets for identical assets or liabilities that the Company is able to access. Since valuations are based on quoted prices that are readily and regularly available in an active market, valuation of such assets or liabilities do not entail a significant degree of judgment. • Level 2—Valuations based on one or more quoted prices in markets that are not active or for which all significant inputs are observable, either directly or indirectly. • Level 3—Valuations based on inputs that are unobservable and significant to the overall fair value measurement.
Commitments and Contingencies	From time to time, the Company may be involved in litigation relating to claims arising out of its operations. The Company is not currently involved in any material legal proceedings. The Company may, however, be involved in material legal proceedings in the future. Such matters are subject to uncertainty and there can be no assurance that such legal proceedings will not have a material adverse effect on its business, results of operations, financial position or cash flows.
Options for Warranty Obligations	The Company’s warranty obligations related to microinverters sold since January 1, 2014 provide the Company the right, but not the requirement, to assign its warranty obligations to a third-party. Under Accounting Standards Codification (“ASC”) 825—Financial Instruments, (“fair value option”), an entity may choose to elect the fair value option for such warranties at the time it first recognizes the eligible item. The Company made an irrevocable election to account for all eligible warranty obligations associated with microinverters sold since January 1, 2014 at fair value. This election was made to reflect the underlying economics of the time value of money for an obligation that will be settled over an extended period of up to 25 years. The Company estimates the fair value of warranty obligations by calculating the warranty obligations in the same manner as for sales prior to January 1, 2014 and applying an expected present value technique to that result. The expected present value technique, an income approach, converts future amounts into a single current discounted amount. In addition to the key estimates of failure rates, claim rates and replacement costs, the Company used certain Level 3 inputs which are unobservable and significant to the overall fair value measurement. Such additional assumptions included a discount rate based on the Company’s credit-adjusted risk-free rate and compensation comprised of a profit element and risk premium required of a market participant to assume the obligation.
Income Taxes	The Company used the discrete tax approach in calculating the tax expense for the three and six months ended June 30, 2018 and 2017 due to the fact that a relatively small change in the Company’s projected pre-tax net income (loss) could result in a volatile effective tax rate. Under the discrete method, the Company determines its tax (expense) benefit based upon actual results as if the interim period was an annual period.
Earnings Per Share	Basic net loss per share is computed by dividing net loss by the weighted average number of shares of common stock outstanding during the period. Diluted loss per share is computed in a similar manner, but it also includes the effect of potential common shares outstanding during the period, when dilutive. Potential common shares include outstanding in-the-money stock options, restricted stock units, shares to be purchased under the Company’s employee stock purchase plan and warrants to purchase common stock. The dilutive effect of potentially dilutive common shares is reflected in diluted earnings per share by application of the treasury stock method. To the extent these potential common shares are antidilutive, they are excluded from the calculation of diluted net loss per share.

REVENUE RECOGNISION (Tables)

REVENUE RECOGNISION (Tables)	6 Months Ended
	Jun. 30, 2018
Revenue from Contract with Customer [Abstract]
Summary of Revenue Disaggregation	The following table provides information about disaggregated revenue by primary geographical market and timing of revenue recognition for the Company’s single product line (in thousands): Three Months Ended June 30, 2018 Six Months Ended June 30, 2018 Primary geographical markets: United States $ 50,258 $ 93,388 International 25,638 52,480 Total $ 75,896 $ 145,868 Timing of revenue recognition: Products transferred at a point in time $ 65,937 $ 125,308 Products and services transferred over time 9,959 20,560 Total $ 75,896 $ 145,868
Summary of Contract Assets and Contract Liabilities, and Changes in Balances from Contracts with Customers	As of June 30, 2018 , receivables, contract assets and contract liabilities from contracts with customers consist of the following (in thousands): June 30, 2018 Receivables $ 58,696 Short-term contract assets (Prepaid expenses and other assets) 13,626 Long-term contract assets (Other assets) 33,134 Short-term contract liabilities (Deferred revenues, current) 34,954 Long-term contract liabilities (Deferred revenues, noncurrent) $ 75,107 Significant changes in the balances of contract liabilities (deferred revenues) and contract assets (prepaid expenses and other assets) during the period are as follows (in thousands): June 30, 2018 Contract Liabilities Balance on January 1, 2018 $ 116,830 Revenue recognized (22,560 ) Increase due to billings 15,791 Balance as of June 30, 2018 $ 110,061 Deferred revenue, current 34,954 Deferred revenue, noncurrent 75,107 Contract Assets Balance on January 1, 2018 $ 47,862 Amount recognized (7,634 ) Increase 6,579 Balance as of June 30, 2018 $ 46,807
Summary of Estimated Revenue Expected to be Recognized in Future Periods	The following table includes estimated revenue expected to be recognized in future periods related to performance obligations that are unsatisfied or partially unsatisfied at the end of the reporting period (in thousands). June 30, 2018 Remainder of 2018 $ 19,849 2019 29,349 2020 23,194 2021 16,997 2022 11,940 Thereafter 8,732 Total $ 110,061
Summary of New Accounting Adoption Impact on Consolidated Statements of Income and Condensed Consolidated Balance Sheets	In accordance with Topic 606, the disclosure of the impact of adoption to the Company’s condensed consolidated statements of operations and condensed consolidated balance sheets was as follows (in thousands): Three Months Ended June 30, 2018 Six Months Ended June 30, 2018 As Reported Adjustments Without Adoption of Topic 606 As Reported Adjustments Without Adoption of Topic 606 Net revenues $ 75,896 $ (2,019 ) $ 73,877 $ 145,868 $ (2,458 ) $ 143,410 Cost of revenues 53,195 (827 ) 52,368 104,851 (996 ) 103,855 Gross profit 22,701 (1,192 ) 21,509 41,017 (1,462 ) 39,555 Operating expenses: Research and development 9,462 — 9,462 17,082 — 17,082 Sales and marketing 6,828 (23 ) 6,805 13,055 (58 ) 12,997 General and administrative 6,969 — 6,969 13,913 — 13,913 Restructuring charges — — — — — — Total operating expenses 23,259 (23 ) 23,236 44,050 (58 ) 43,992 Loss from operations (558 ) (1,169 ) (1,727 ) (3,033 ) (1,404 ) (4,437 ) Other expense, net: Interest expense (2,269 ) — (2,269 ) (4,562 ) — (4,562 ) Other income (expense) (572 ) — (572 ) (698 ) — (698 ) Total other expense, net (2,841 ) — (2,841 ) (5,260 ) — (5,260 ) Loss before income taxes (3,399 ) (1,169 ) (4,568 ) (8,293 ) (1,404 ) (9,697 ) Provision for income taxes (339 ) — (339 ) (573 ) — (573 ) Net loss $ (3,738 ) $ (1,169 ) $ (4,907 ) $ (8,866 ) $ (1,404 ) $ (10,270 ) Net loss per share: Basic and diluted $ (0.04 ) $ (0.01 ) $ (0.05 ) $ (0.09 ) $ (0.02 ) $ (0.11 ) Shares used in per share calculation: Basic and diluted 97,321 97,321 94,026 94,026 June 30, 2018 As Reported Adjustments Without Adoption of Topic 606 Prepaid expenses and other $ 20,741 $ (9,878 ) $ 10,863 Other assets 36,030 (27,856 ) 8,174 Accrued liabilities 31,095 (5,180 ) 25,915 Deferred revenues 34,954 (19,884 ) 15,070 Deferred revenues, noncurrent 75,107 (50,210 ) 24,897 Accumulated deficit $ (343,541 ) $ 37,540 $ (306,001 )

INVENTORY (Tables)

INVENTORY (Tables)	6 Months Ended
	Jun. 30, 2018
Inventory Disclosure [Abstract]
Summary of Inventory	Inventory as of June 30, 2018 and December 31, 2017 consists of the following (in thousands): June 30, December 31, Raw materials $ 2,889 $ 2,341 Finished goods 14,582 23,658 Total inventory $ 17,471 $ 25,999

WARRANTY OBLIGATIONS (Tables)

WARRANTY OBLIGATIONS (Tables)	6 Months Ended
	Jun. 30, 2018
Product Warranties Disclosures [Abstract]
Summary of Warranty Activities	The Company’s warranty activities during the three and six months ended June 30, 2018 and 2017 were as follows (in thousands): Three Months Ended Six Months Ended 2018 2017 2018 2017 Warranty obligations, beginning of period $ 30,625 $ 31,995 $ 29,816 $ 31,414 Accruals for warranties issued during period 775 1,089 1,533 1,921 Changes in estimates 1,378 (91 ) 2,828 203 Settlements (2,099 ) (1,981 ) (3,775 ) (3,598 ) Increase due to accretion expense 520 499 939 993 Other 443 102 301 680 Warranty obligations, end of period $ 31,642 $ 31,613 $ 31,642 $ 31,613 Less current portion $ (8,275 ) $ (8,032 ) Noncurrent $ 23,367 $ 23,581

FAIR VALUE MEASUREMENTS (Tables

FAIR VALUE MEASUREMENTS (Tables)	6 Months Ended
	Jun. 30, 2018
Fair Value Disclosures [Abstract]
Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis	The following table presents the Company’s liabilities that were measured at fair value on a recurring basis and its categorization within the fair value hierarchy at June 30, 2018 and December 31, 2017 (in thousands): Fair Value June 30, December 31, Liabilities: Warranty obligations Level 3 $ 12,836 $ 9,790 Third party option to purchase receivables at a discount Level 3 — 700
Schedule of Changes in Nonfinancial Liabilities Related to Warrant Obligations Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs	The following table provides information regarding changes in nonfinancial liabilities related to the Company’s warranty obligations measured at fair value on a recurring basis using significant unobservable inputs (Level 3) for the periods indicated (in thousands): Three Months Ended Six Months Ended 2018 2017 2018 2017 Balance at beginning of period $ 11,719 $ 11,627 $ 9,790 $ 10,332 Accruals for warranties issued during period 775 1,080 1,533 1,910 Changes in estimates 210 (351 ) 1,995 (617 ) Settlements (831 ) (393 ) (1,722 ) (735 ) Increase due to accretion expense 520 499 939 994 Other 443 102 301 680 Balance at end of period $ 12,836 $ 12,564 $ 12,836 $ 12,564
Summary of Significant Unobservable Inputs used in the Fair Value Measurement of Liabilities Designated as Level 3	As of June 30, 2018 , the significant unobservable inputs used in the fair value measurement of the Company’s liabilities designated as Level 3 are as follows: Item Measured at Fair Value Valuation Technique Description of Significant Unobservable Input Percent Used (Weighted-Average) Warranty obligations for microinverters sold since January 1, 2014 Discounted cash flows Profit element and risk premium 16% Credit-adjusted risk-free rate 16% As of December 31, 2017 , the significant unobservable inputs used in the fair value measurement of the Company’s liabilities designated as Level 3 are as follows: Item Measured at Fair Value Valuation Technique Description of Significant Unobservable Input Percent Used (Weighted-Average) Warranty obligations for microinverters sold since January 1, 2014 Discounted cash flows Profit element and risk premium 17% Credit-adjusted risk-free rate 17% Third party option to purchase receivables at a discount Discounted cash flows Counter party credit-adjusted risk-free rate 4%

GOODWILL AND INTANGIBLE ASSETS

GOODWILL AND INTANGIBLE ASSETS (Tables)	6 Months Ended
	Jun. 30, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill and Intangible Assets	The following table presents the details of the Company’s goodwill and purchased intangible assets as of June 30, 2018 and December 31, 2017 (in thousands): June 30, 2018 December 31, 2017 Gross Accumulated Amortization Net Gross Accumulated Amortization Net Goodwill $ 3,664 $ — $ 3,664 $ 3,664 $ — $ 3,664 Other indefinite-lived intangibles $ 286 $ — $ 286 $ 286 $ — $ 286 Intangible assets with finite lives: Patents and licensed technology 1,665 (1,588 ) 77 1,665 (1,436 ) 229 Total purchased intangible assets $ 1,951 $ (1,588 ) $ 363 $ 1,951 $ (1,436 ) $ 515

RESTRUCTURING (Tables)

RESTRUCTURING (Tables)	6 Months Ended
	Jun. 30, 2018
Restructuring and Related Activities [Abstract]
Restructuring and Related Costs	The following table presents the details of the Company’s restructuring charges for the periods indicated (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2018 2017 2018 2017 Employee severance and benefit arrangements $ — $ 123 $ — $ 1,715 Asset impairments — — — 522 Consultants engaged in restructuring activities — 3,000 — 7,000 Lease loss reserves and contract termination costs — 486 — 1,619 Total restructuring and asset impairment charges $ — $ 3,609 $ — $ 10,856
Schedule of Restructuring Reserve by Type of Cost	The following table provides information regarding changes in the Company’s accrued restructuring balance for the periods indicated (in thousands): Employee Severance and Benefits Lease Loss Reserves and Contractual Obligations Total Balance at end of period as of December 31, 2017 $ 229 $ 1,094 $ 1,323 Cash payments and receipts, net (229 ) 54 (175 ) Balance at end of period as of June 30, 2018 $ 0 $ 1,148 $ 1,148

DEBT (Tables)

DEBT (Tables)	6 Months Ended
	Jun. 30, 2018
Debt Disclosure [Abstract]
Schedule of Maturities of Long-term Debt	As of June 30, 2018 , the estimated schedule of principal payments due on the term loan is as follows (in thousands): Year Amounts 2018 $ 4,779 2019 25,238 2020 16,854 Total $ 46,871
Schedule of Debt	Long-term debt was comprised of the following at June 30, 2018 and December 31, 2017 (in thousands): June 30, December 31, Term loan $ 46,871 $ 50,000 Less unamortized discount and issuance costs (1,557 ) (2,111 ) Carrying amount of term loan 45,314 47,889 Sale of long term financing receivable recorded as debt 6,674 2,562 Less value of future purchase option — (700 ) Carrying amount of sale of long term financing receivable recorded as debt 6,674 1,862 Total carrying amount of debt 51,988 49,751 Less current portion term loan (16,380 ) (15,715 ) Less current portion of long term financing receivable recorded as debt (2,049 ) (1,714 ) Long-term debt $ 33,559 $ 32,322

STOCK-BASED COMPENSATION (Table

STOCK-BASED COMPENSATION (Tables)	6 Months Ended
	Jun. 30, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of Stock Option Activity	The following is a summary of stock option activity for the six months ended June 30, 2018 (in thousands, except per share data): Number of Shares Outstanding Weighted- Average Exercise Price per Share Outstanding at December 31, 2017 8,426 $ 1.77 Granted 213 4.43 Exercised (803 ) 1.73 Canceled (149 ) 5.06 Outstanding at June 30, 2018 7,687 $ 1.78
Summary of Restricted Stock Unit Activity	The following is a summary of restricted stock unit (“RSU”) and performance stock unit (“PSU”) activity for the six months ended June 30, 2018 (in thousands, except per share data): RSUs and PSUs Weighted Average Outstanding at December 31, 2017 3,505 $ 2.03 Granted 3,536 3.47 Vested (702 ) 2.52 Canceled (250 ) 2.19 Outstanding at June 30, 2018 6,089 $ 2.80
Summary of the Components of Total Stock-Based Compensation Expense	The following table summarizes the components of total stock-based compensation expense included in the condensed consolidated statements of operations for the periods presented (in thousands): Three Months Ended Six Months Ended 2018 2017 2018 2017 Cost of revenues $ 417 $ 211 $ 615 $ 449 Research and development 1,149 636 1,767 1,387 Sales and marketing 997 285 1,358 663 General and administrative 1,725 489 2,120 1,051 Total $ 4,288 $ 1,621 $ 5,860 $ 3,550
Summary of Stock-Based Compensation Associated with Each Type of Award	The following table summarizes the various types of stock-based compensation expense for the periods presented (in thousands): Three Months Ended Six Months Ended 2018 2017 2018 2017 Stock options and RSUs and PSUs $ 3,975 $ 1,291 $ 5,293 $ 2,890 Employee stock purchase plan 313 330 567 660 Total $ 4,288 $ 1,621 $ 5,860 $ 3,550
Summary of the Weighted-Average Grant Date Fair Value of Options Granted	The following table presents the weighted-average grant date fair value of options granted for the periods presented and the assumptions used to estimate those values using a Black-Scholes option pricing model: Three Months Ended Six Months Ended 2018 2017 2018 2017 Weighted average grant date fair value $ 3.51 $ 0.71 $ 2.74 $ 0.71 Expected term (in years) 3.8 4.6 4.0 4.6 Expected volatility 89.7 % 84.9 % 88.1 % 85.0 % Annual risk-free rate of return 2.7 % 1.8 % 2.6 % 1.8 % Dividend yield 0.0 % 0.0 % 0.0 % 0.0 %

NET LOSS PER SHARE (Tables)

NET LOSS PER SHARE (Tables)	6 Months Ended
	Jun. 30, 2018
Earnings Per Share [Abstract]
Schedule of Computation of Basic and Diluted Net Loss Per Share	The following table presents the computation of basic and diluted net loss per share for the periods presented (in thousands, except per share data): Three Months Ended Six Months Ended 2018 2017 2018 2017 Numerator: Net loss $ (3,738 ) $ (12,093 ) $ (8,866 ) $ (35,398 ) Denominator: Weighted average common shares outstanding 97,321 84,434 94,026 80,542 Net loss per share, basic and diluted $ (0.04 ) $ (0.14 ) $ (0.09 ) $ (0.44 )
Schedule of Potentially Dilutive Securities Excluded from the Computation of Diluted Net Loss Per Share	The following table sets forth the potentially dilutive securities excluded from the computation of the diluted net loss per share (in thousands): Three Months Ended Six Months Ended 2018 2017 2018 2017 Employee stock options 8,102 8,068 8,259 8,262 RSUs and PSUs 5,710 2,017 4,690 1,276 Warrants to purchase common stock — 1,220 — 944 Total 13,812 11,305 12,949 10,482

DESCRIPTION OF BUSINESS AND B30

DESCRIPTION OF BUSINESS AND BASIS OF PRESENTATION (Details) system in Thousands, deliverable in Millions, watt in Billions	Jun. 30, 2018countrysystemdeliverablewatt
Product Information [Line Items]
Number of countries in which product is deployed (country) | country	120
Microinverter
Product Information [Line Items]
Number of product shipped (deliverable) | deliverable	17
Number of watts (watt) | watt	4
Residential and Commercial Systems
Product Information [Line Items]
Number of product deployed (system) | system	790

REVENUE RECOGNISION - Narrative

REVENUE RECOGNISION - Narrative (Details)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2018USD ($)	Jun. 30, 2017USD ($)	Jun. 30, 2018USD ($)	Jun. 30, 2017USD ($)	Dec. 31, 2017USD ($)accounting_unit	Jan. 01, 2018USD ($)
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accumulated deficit increase (reduction)	$ (343,541,000)		$ (343,541,000)		$ (295,727,000)
Net increase in revenues	75,896,000	$ 74,704,000	145,868,000	$ 129,455,000
Number of accounting units (accounting unit) | accounting_unit					2
Increase in deferred revenue	110,061,000		110,061,000			$ 116,830,000
Accrued liabilities	31,095,000		31,095,000		$ 22,447,000
Contract asset impairment charges	0
Products and services transferred over time
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net increase in revenues	9,959,000		20,560,000
Products transferred at a point in time
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net increase in revenues	$ 65,937,000		$ 125,308,000
Monitoring Hardware and Service | Incurred Commissions
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Amortization period for capitalized costs						6 years 6 months
Envoy Communications Gateway | Products and services transferred over time
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue recognition period	6 years 6 months		6 years 6 months
Communication Accessories | Minimum | Products transferred at a point in time
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue recognition period	5 years		5 years
Communication Accessories | Maximum | Products transferred at a point in time
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenue recognition period	12 years		12 years
Adjustments | Incurred Commissions
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Increase in deferred costs						$ 800,000
Adjustments | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accumulated deficit increase (reduction)	$ (37,540,000)		$ (37,540,000)			(38,900,000)
Net increase in revenues	2,019,000		2,458,000
Accrued liabilities	$ 5,180,000		$ 5,180,000			5,600,000
Adjustments | Accounting Standards Update 2014-09 | Envoy Communications Device and Enlighten Service
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accumulated deficit increase (reduction)						34,100,000
Increase in deferred revenue						77,500,000
Increase in deferred costs						43,400,000
Unbilled revenue						6,400,000
Adjustments | Accounting Standards Update 2014-09 | Monitoring Hardware and Service | Incurred Commissions
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Accumulated deficit increase (reduction)						$ (800,000)

REVENUE RECOGNISION - Summary o

REVENUE RECOGNISION - Summary of Disaggregated Revenue by Primary Geographical Market and Timing of Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenues	$ 75,896	$ 74,704	$ 145,868	$ 129,455
Products transferred at a point in time
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenues	65,937		125,308
Products and services transferred over time
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenues	9,959		20,560
United States
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenues	50,258		93,388
International
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenues	$ 25,638		$ 52,480

REVENUE RECOGNISION - Summary33

REVENUE RECOGNISION - Summary of Contract Assets and Contract Liabilities from Contracts with Customers (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Revenue from Contract with Customer [Abstract]
Receivables	$ 58,696	$ 65,346
Short-term contract assets (Prepaid expenses and other assets)	13,626
Long-term contract assets (Other assets)	33,134
Short-term contract liabilities (Deferred revenues, current)	34,954	15,691
Long-term contract liabilities (Deferred revenues, noncurrent)	$ 75,107	$ 29,941

REVENUE RECOGNISION - Summary34

REVENUE RECOGNISION - Summary of Significant Changes in the Balances of Contract Liabilities (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Contract Liabilities
Balance, beginning of period	$ 116,830
Revenue recognized	(22,560)
Increase due to billings	15,791
Balance, end of period	110,061
Deferred revenues, current	34,954	$ 15,691
Deferred revenues, noncurrent	75,107	$ 29,941
Contract Assets
Balance, beginning of period	47,862
Amount recognized	(7,634)
Increase	6,579
Balance, end of period	$ 46,807

REVENUE RECOGNISION - Summary35

REVENUE RECOGNISION - Summary of Estimated Revenue Expected to be Recognized in Future Periods (Details) $ in Thousands	Jun. 30, 2018USD ($)
Revenue from Contract with Customer [Abstract]
Total estimated revenue expected to be recognized in future periods	$ 110,061
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2018-07-01
Revenue from Contract with Customer [Abstract]
Total estimated revenue expected to be recognized in future periods	$ 19,849
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total estimated revenue expected to be recognized in future periods, expected timing	9 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue from Contract with Customer [Abstract]
Total estimated revenue expected to be recognized in future periods	$ 29,349
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total estimated revenue expected to be recognized in future periods, expected timing	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue from Contract with Customer [Abstract]
Total estimated revenue expected to be recognized in future periods	$ 23,194
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total estimated revenue expected to be recognized in future periods, expected timing	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue from Contract with Customer [Abstract]
Total estimated revenue expected to be recognized in future periods	$ 16,997
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total estimated revenue expected to be recognized in future periods, expected timing	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue from Contract with Customer [Abstract]
Total estimated revenue expected to be recognized in future periods	$ 8,732
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total estimated revenue expected to be recognized in future periods, expected timing	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-02
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Total estimated revenue expected to be recognized in future periods, expected timing

REVENUE RECOGNISION - Summary36

REVENUE RECOGNISION - Summary of New Accounting Adoption Impact on Consolidated Statements of Income (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenues	$ 75,896	$ 74,704	$ 145,868	$ 129,455
Cost of revenues	53,195	61,157	104,851	108,861
Gross profit	22,701	13,547	41,017	20,594
Operating expenses:
Research and development	9,462	7,947	17,082	17,552
Sales and marketing	6,828	6,274	13,055	12,732
General and administrative	6,969	4,964	13,913	10,797
Restructuring charges	0	3,609	0	10,856
Total operating expenses	23,259	22,794	44,050	51,937
Loss from operations	(558)	(9,247)	(3,033)	(31,343)
Other expense, net:
Interest Expense	(2,269)	(2,080)	(4,562)	(4,219)
Other income (expense)	(572)	88	(698)	1,148
Total other expense, net	(2,841)	(1,992)	(5,260)	(3,071)
Loss before income taxes	(3,399)	(11,239)	(8,293)	(34,414)
Provision for income taxes	(339)	(854)	(573)	(984)
Net loss	$ (3,738)	$ (12,093)	$ (8,866)	$ (35,398)
Net loss per share:
Basic and diluted (in usd per share)	$ (0.04)	$ (0.14)	$ (0.09)	$ (0.44)
Shares used in per share calculation:
Basic and diluted (in shares)	97,321	84,434	94,026	80,542
Adjustments | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenues	$ 2,019		$ 2,458
Cost of revenues	827		996
Gross profit	1,192		1,462
Operating expenses:
Research and development	0		0
Sales and marketing	23		58
General and administrative	0		0
Restructuring charges	0		0
Total operating expenses	23		58
Loss from operations	1,169		1,404
Other expense, net:
Interest Expense	0		0
Other income (expense)	0		0
Total other expense, net	0		0
Loss before income taxes	1,169		1,404
Provision for income taxes	0		0
Net loss	$ 1,169		$ 1,404
Net loss per share:
Basic and diluted (in usd per share)	$ 0.01		$ 0.02
Without Adoption of Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Net revenues	$ 73,877		$ 143,410
Cost of revenues	52,368		103,855
Gross profit	21,509		39,555
Operating expenses:
Research and development	9,462		17,082
Sales and marketing	6,805		12,997
General and administrative	6,969		13,913
Restructuring charges	0		0
Total operating expenses	23,236		43,992
Loss from operations	(1,727)		(4,437)
Other expense, net:
Interest Expense	(2,269)		(4,562)
Other income (expense)	(572)		(698)
Total other expense, net	(2,841)		(5,260)
Loss before income taxes	(4,568)		(9,697)
Provision for income taxes	(339)		(573)
Net loss	$ (4,907)		$ (10,270)
Net loss per share:
Basic and diluted (in usd per share)	$ (0.05)		$ (0.11)
Shares used in per share calculation:
Basic and diluted (in shares)	97,321		94,026

REVENUE RECOGNISION - Summary37

REVENUE RECOGNISION - Summary of New Accounting Adoption Impact on Condensed Consolidated Balance Sheets (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Prepaid expenses and other assets	$ 20,741		$ 9,957
Other assets	36,030		8,039
Accrued liabilities	31,095		22,447
Deferred revenues, current	34,954		15,691
Deferred revenues, noncurrent	75,107		29,941
Accumulated deficit	(343,541)		$ (295,727)
Adjustments | Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Prepaid expenses and other assets	9,878
Other assets	27,856
Accrued liabilities	5,180	$ 5,600
Deferred revenues, current	19,884
Deferred revenues, noncurrent	50,210
Accumulated deficit	(37,540)	$ (38,900)
Without Adoption of Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Prepaid expenses and other assets	10,863
Other assets	8,174
Accrued liabilities	25,915
Deferred revenues, current	15,070
Deferred revenues, noncurrent	24,897
Accumulated deficit	$ (306,001)

INVENTORY - Summary of Inventor

INVENTORY - Summary of Inventory (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Schedule of inventory
Raw materials	$ 2,889	$ 2,341
Finished goods	14,582	23,658
Total inventory	$ 17,471	$ 25,999

WARRANTY OBLIGATIONS - Summary

WARRANTY OBLIGATIONS - Summary of Warranty Activities (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Changes in the Company's product warranty liability
Warranty obligations, beginning of period	$ 30,625	$ 31,995	$ 29,816	$ 31,414
Accruals for warranties issued during period	775	1,089	1,533	1,921
Changes in estimates	1,378	(91)	2,828	203
Settlements	(2,099)	(1,981)	(3,775)	(3,598)
Increase due to accretion expense	520	499	939	993
Other	443	102	301	680
Warranty obligations, end of period	31,642	31,613	31,642	31,613
Less current portion	(8,275)	(8,032)	(8,275)	(8,032)	$ (7,427)
Noncurrent	$ 23,367	$ 23,581	$ 23,367	$ 23,581	$ 22,389

WARRANTY OBLIGATIONS - Narrativ

WARRANTY OBLIGATIONS - Narrative (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016
Product Warranty Liability [Line Items]
Warranty obligations	$ 31,642	$ 30,625	$ 29,816	$ 31,613	$ 31,995	$ 31,414
Recurring | Warranty obligations for microinverters sold since January 1, 2014 | Level 3
Product Warranty Liability [Line Items]
Fair value liabilities	$ 12,836	$ 11,719	$ 9,790	$ 12,564	$ 11,627	$ 10,332

FAIR VALUE MEASUREMENTS - Sched

FAIR VALUE MEASUREMENTS - Schedule of Assets and Liabilities Measured at Fair Value on a Recurring Basis (Details) - Recurring - Level 3 - USD ($) $ in Thousands	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016
Warranty obligations for microinverters sold since January 1, 2014
Liabilities:
Fair value liabilities	$ 12,836	$ 11,719	$ 9,790	$ 12,564	$ 11,627	$ 10,332
Third party option to purchase receivables at a discount
Liabilities:
Fair value liabilities	$ 0		$ 700

FAIR VALUE MEASUREMENTS - Sch42

FAIR VALUE MEASUREMENTS - Schedule of Changes in Nonfinancial Liabilities Related to Warrant Obligations Measured at Fair Value on a Recurring Basis Using Significant Unobservable Inputs (Details) - Level 3 - Recurring - Warranty obligations - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of period	$ 11,719	$ 11,627	$ 9,790	$ 10,332
Accruals for warranties issued during period	775	1,080	1,533	1,910
Changes in estimates	210	(351)	1,995	(617)
Settlements	(831)	(393)	(1,722)	(735)
Increase due to accretion expense	520	499	939	994
Other	443	102	301	680
Balance at end of period	$ 12,836	$ 12,564	$ 12,836	$ 12,564

FAIR VALUE MEASUREMENTS - Summa

FAIR VALUE MEASUREMENTS - Summary of Significant Unobservable Inputs used in the Fair Value Measurement of Liabilities Designated as Level 3 (Details) - Recurring - Level 3	Jun. 30, 2018	Dec. 31, 2017
Measurement Input, Profit Element and Risk Premium | Warranty obligations for microinverters sold since January 1, 2014
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warranty obligations for microinverters sold since January 1, 2014	0.16	0.17
Measurement Input, Entity Credit Risk | Warranty obligations for microinverters sold since January 1, 2014
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Warranty obligations for microinverters sold since January 1, 2014	0.16	0.17
Measurement Input, Counterparty Credit Risk | Third party option to purchase receivables at a discount
Fair Value Measurement Inputs and Valuation Techniques [Line Items]
Third party option to purchase receivables at a discount		0.04

FAIR VALUE MEASUREMENTS - Narra

FAIR VALUE MEASUREMENTS - Narrative (Details) - Discounted cash flows - Recurring - Level 3 - Contingent consideration $ in Millions	6 Months Ended
	Jun. 30, 2018USD ($)
Derivative [Line Items]
Decrease to fair value measurement as a result of 100 basis point increase	$ 0.6
Increase to fair value measurement as a result of 100 basis point decrease	$ 0.6

GOODWILL AND INTANGIBLE ASSET45

GOODWILL AND INTANGIBLE ASSETS - Schedule of Goodwill and Intangible Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Goodwill, gross	$ 3,664	$ 3,664
Goodwill, net	3,664	3,664
Other indefinite-lived intangibles	286	286
Intangible assets with finite lives:
Intangibles assets with finite lives, gross	1,951	1,951
Intangibles assets with finite lives, accumulated amortization	(1,588)	(1,436)
Total	363	515
Patents and licensed technology
Intangible assets with finite lives:
Intangibles assets with finite lives, gross	1,665	1,665
Intangibles assets with finite lives, accumulated amortization	(1,588)	(1,436)
Total	$ 77	$ 229

GOODWILL AND INTANGIBLE ASSET46

GOODWILL AND INTANGIBLE ASSETS - Narrative (Details) - USD ($) $ in Millions	1 Months Ended		6 Months Ended
	Oct. 31, 2015	Jul. 31, 2014	Jun. 30, 2018
Finite-Lived Intangible Assets [Line Items]
Amortization expense related to intangible assets			$ 0.1
Patents
Finite-Lived Intangible Assets [Line Items]
Useful life		3 years
ASIC development
Finite-Lived Intangible Assets [Line Items]
Useful life	3 years
Patents and licensed technology
Finite-Lived Intangible Assets [Line Items]
Patents and licensed technology amortized during the remainder of 2018			$ 0.1

RESTRUCTURING - Summary of Rest

RESTRUCTURING - Summary of Restructuring Charges (Details) - Restructuring Plan 2016 - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Restructuring Cost and Reserve [Line Items]
Total restructuring and asset impairment charges	$ 0	$ 3,609	$ 0	$ 10,856
Employee severance and benefit arrangements
Restructuring Cost and Reserve [Line Items]
Total restructuring and asset impairment charges	0	123	0	1,715
Asset impairments
Restructuring Cost and Reserve [Line Items]
Total restructuring and asset impairment charges	0	0	0	522
Consultants engaged in restructuring activities
Restructuring Cost and Reserve [Line Items]
Total restructuring and asset impairment charges	0	3,000	0	7,000
Lease loss reserves and contract termination costs
Restructuring Cost and Reserve [Line Items]
Total restructuring and asset impairment charges	$ 0	$ 486	$ 0	$ 1,619

RESTRUCTURING - Rollforward (De

RESTRUCTURING - Rollforward (Details) - Restructuring Plan 2016 $ in Thousands	6 Months Ended
	Jun. 30, 2018USD ($)
Restructuring Reserve [Roll Forward]
Restructuring reserve, Beginning balance	$ 1,323
Cash payments	(175)
Restructuring reserve, Ending balance	1,148
Employee Severance and Benefits
Restructuring Reserve [Roll Forward]
Restructuring reserve, Beginning balance	229
Cash payments	(229)
Restructuring reserve, Ending balance	0
Lease Loss Reserves and Contractual Obligations
Restructuring Reserve [Roll Forward]
Restructuring reserve, Beginning balance	1,094
Cash payments	54
Restructuring reserve, Ending balance	$ 1,148

DEBT - Narrative (Details)

DEBT - Narrative (Details)	Feb. 28, 2018USD ($)$ / sharesshares	Feb. 28, 2018USD ($)$ / sharesshares	Dec. 31, 2017USD ($)	Feb. 28, 2017USD ($)	Jul. 31, 2016USD ($)	Jun. 30, 2018USD ($)shares	Jun. 30, 2017USD ($)	Dec. 31, 2016USD ($)	Nov. 30, 2012USD ($)
Short-term Debt [Line Items]
Proceeds from debt						$ 5,580,000	$ 24,240,000
Payments under revolving credit facility						0	10,100,000
Fair value of warrants issued	$ 1,400,000	$ 1,400,000				0	$ 1,447,000
Value of future purchase option			$ 700,000
Cashless Exercise Warrants | Measurement Input, Quoted Price
Short-term Debt [Line Items]
Warrants and rights, measurement input | $ / shares	1.05	1.05
Cashless Exercise Warrants | Measurement Input, Share Price
Short-term Debt [Line Items]
Warrants and rights, measurement input | $ / shares	1.56	1.56
Cashless Exercise Warrants | Measurement Input, Price Volatility
Short-term Debt [Line Items]
Warrants and rights, measurement input	0.859	0.859
Cashless Exercise Warrants | Measurement Input, Risk Free Interest Rate
Short-term Debt [Line Items]
Warrants and rights, measurement input	0.0223	0.0223
Cashless Exercise Warrants | Measurement Input, Expected Dividend Rate
Short-term Debt [Line Items]
Warrants and rights, measurement input	0	0
Cashless Exercise Warrants | Measurement Input, Expected Term
Short-term Debt [Line Items]
Warrants and rights outstanding, term	7 years	7 years
Secured Debt | Amended Term Loan Agreement, February 2017 | Closing Date to March 31, 2018
Short-term Debt [Line Items]
Liquidity ratio required		1.5
Secured Debt | Amended Term Loan Agreement, February 2017 | April 1, 2018 and Thereafter
Short-term Debt [Line Items]
Liquidity ratio required		1.75
Financing Receivable | Financing Receivable Recorded as Debt
Short-term Debt [Line Items]
Proceeds from debt			$ 2,800,000			$ 5,600,000
Secured Debt | Second Amendment To Term Loans
Short-term Debt [Line Items]
Percent decrease in principal payments	50.00%
Tennenbaum Capital Partners, LLC | Secured Debt | Amended Term Loan Agreement, February 2017
Short-term Debt [Line Items]
Interest rate during period				10.3125%
Commitment fee percentage				3.00%
Closing fee				4.00%
Unrestricted cash		$ 10,000,000
Number of securities called by warrants (in shares) | shares	1,220,000	1,220,000				912,067
Class of warrant term year		7 years
Tennenbaum Capital Partners, LLC | Secured Debt | Amended Term Loan Agreement, February 2017 | Measurement Input, Quoted Price
Short-term Debt [Line Items]
Warrants and rights, measurement input | $ / shares	1.05	1.05
Tennenbaum Capital Partners, LLC | Secured Debt | Term Loan Agreement, July 2016
Short-term Debt [Line Items]
Debt instrument face amount					$ 25,000,000
Tennenbaum Capital Partners, LLC | Secured Debt | Minimum | Amended Term Loan Agreement, February 2017
Short-term Debt [Line Items]
Prepayment fee				1.00%
Tennenbaum Capital Partners, LLC | Secured Debt | Maximum | Amended Term Loan Agreement, February 2017
Short-term Debt [Line Items]
Prepayment fee				3.00%
Tennenbaum Capital Partners, LLC | Secured Debt | LIBOR | Amended Term Loan Agreement, February 2017
Short-term Debt [Line Items]
Basis spread on variable rate				9.25%
Tennenbaum Capital Partners, LLC | Secured Debt
Short-term Debt [Line Items]
Debt instrument face amount					25,000,000
Proceeds from debt					$ 25,000,000
Interest rate during period					10.25%
Commitment fee percentage					3.30%
Closing fee					10.00%
Tennenbaum Capital Partners, LLC | Secured Debt | Amended Term Loan Agreement, February 2017
Short-term Debt [Line Items]
Debt instrument face amount				$ 25,000,000
Tennenbaum Capital Partners, LLC | Secured Debt | Minimum
Short-term Debt [Line Items]
Prepayment fee					1.00%
Tennenbaum Capital Partners, LLC | Secured Debt | Maximum
Short-term Debt [Line Items]
Prepayment fee					3.00%
Tennenbaum Capital Partners, LLC | Secured Debt | LIBOR
Short-term Debt [Line Items]
Interest rate during period					9.5625%
Reduction of interest rate during period					1.00%
Wells Fargo Bank | Revolving Credit Facility | Line of Credit
Short-term Debt [Line Items]
Payments under revolving credit facility					$ 10,300,000
Maximum borrowing capacity									$ 50,000,000
Revolving credit facility								$ 10,100,000

DEBT - Maturities (Details)

DEBT - Maturities (Details) - Secured Debt - Second Amendment To Term Loans $ in Thousands	Jun. 30, 2018USD ($)
Debt Instrument [Line Items]
2,018	$ 4,779
2,019	25,238
2,020	16,854
Total	$ 46,871

DEBT - Long term debt (Details)

DEBT - Long term debt (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Total carrying amount of debt	$ 51,988	$ 49,751
Debt, current	(18,429)	(17,429)
Debt, noncurrent	33,559	32,322
Secured Debt | Term Loan Agreement, July 2016
Debt Instrument [Line Items]
Term loan	46,871	50,000
Less unamortized discount and issuance costs	(1,557)	(2,111)
Total carrying amount of debt	45,314	47,889
Debt, current	(16,380)	(15,715)
Financing Receivable | Financing Receivable Recorded as Debt
Debt Instrument [Line Items]
Term loan	6,674	2,562
Less value of future purchase option	0	(700)
Total carrying amount of debt	6,674	1,862
Debt, current	$ (2,049)	$ (1,714)

COMMITMENTS AND CONTINGENCIES -

COMMITMENTS AND CONTINGENCIES - Narrative (Details) - USD ($)	3 Months Ended
	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018
Intellectual Property, Technology and Other Assets | Forecast
Schedule Of Asset Acquisitions, By Acquisition [Line Items]
Cash consideration	$ 15,000,000
Common stock issuable in asset acquisition (shares)	7,500,000
Additional cash consideration	$ 10,000,000
Additional cash consideration, period	4 months
Loss on Long-term Purchase Commitment
Schedule Of Asset Acquisitions, By Acquisition [Line Items]
Accrual for legal settlements			$ 2,000,000
Payments for legal settlements		$ 1,800,000

SALE OF COMMON STOCK (Details)

SALE OF COMMON STOCK (Details) - USD ($) $ / shares in Units, $ in Thousands	Feb. 04, 2018	Jun. 30, 2018	Jun. 30, 2017
Subsidiary, Sale of Stock [Line Items]
Proceeds from issuance of common stock		$ 19,923	$ 26,425
Private Placement
Subsidiary, Sale of Stock [Line Items]
Number of shares issued (in shares)	9,523,809
Price per share issued (in usd per share)	$ 2.10
Proceeds from issuance of common stock	$ 20,000

STOCK-BASED COMPENSATION - Summ

STOCK-BASED COMPENSATION - Summary of Stock Option Activity (Details) shares in Thousands	6 Months Ended
	Jun. 30, 2018$ / sharesshares
Number of Shares Outstanding
Outstanding, beginning balance (in shares) | shares	8,426
Granted (in shares) | shares	213
Exercised (in shares) | shares	(803)
Canceled (in shares) | shares	(149)
Outstanding, ending balance (in shares) | shares	7,687
Weighted- Average Exercise Price per Share
Outstanding, beginning balance (in usd per share) | $ / shares	$ 1.77
Granted (in usd per share) | $ / shares	4.43
Exercised (in usd per share) | $ / shares	1.73
Canceled (in usd per share) | $ / shares	5.06
Outstanding, ending balance (in usd per share) | $ / shares	$ 1.78

STOCK-BASED COMPENSATION - Narr

STOCK-BASED COMPENSATION - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	Apr. 03, 2017	Jun. 30, 2018	Jun. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic value of options exercised			$ 3
Intrinsic value of options outstanding		$ 38.6	$ 38.6
Common stock to be purchased in exchange for options (in shares)			149,000
Total unrecognized compensation cost		16.8	$ 16.8
Weighted-average recognition period for unrecognized compensation cost			2 years 8 months 12 days
Tender Offer, Exchange Out of the Money Stock Optionsfor Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award granted (in shares)	733,559
Common stock to be purchased in exchange for options (in shares)	2,362,470
Restricted stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of stock vested during period			$ 3
Intrinsic value of restricted stock units outstanding		$ 41	$ 41
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award granted (in shares)		1,400,000
Weighted average estimated fair value of award (in usd per share)		$ 4.57
Performance Shares | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance target percentage		0.00%
Performance Shares | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance target percentage		150.00%
Performance Shares with Market Conditions
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award granted (in shares)		720,000
Weighted average estimated fair value of award (in usd per share)		$ 4.54

STOCK-BASED COMPENSATION - Su56

STOCK-BASED COMPENSATION - Summary of Restricted Stock Unit Activity (Details) - Restricted stock units shares in Thousands	6 Months Ended
	Jun. 30, 2018$ / sharesshares
RSUs and PSUs
Outstanding, beginning balance (in shares) | shares	3,505
Granted (in shares) | shares	3,536
Vested (in shares) | shares	(702)
Canceled (in shares) | shares	(250)
Outstanding, ending balance (in shares) | shares	6,089
Weighted Average Fair Value per Share at Grant Date
Outstanding, beginning balance (in usd per share) | $ / shares	$ 2.03
Granted (in usd per share) | $ / shares	3.47
Vested (in usd per share) | $ / shares	2.52
Canceled (in usd per share) | $ / shares	2.19
Outstanding, ending balance (in usd per share) | $ / shares	$ 2.80

STOCK-BASED COMPENSATION - Su57

STOCK-BASED COMPENSATION - Summary of the Components of Total Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Allocation of Stock-based Compensation Expense Included in the Consolidated Statement of Operations [Abstract]
Total stock-based compensation expense	$ 4,288	$ 1,621	$ 5,860	$ 3,550
Cost of revenues
Allocation of Stock-based Compensation Expense Included in the Consolidated Statement of Operations [Abstract]
Total stock-based compensation expense	417	211	615	449
Research and development
Allocation of Stock-based Compensation Expense Included in the Consolidated Statement of Operations [Abstract]
Total stock-based compensation expense	1,149	636	1,767	1,387
Sales and marketing
Allocation of Stock-based Compensation Expense Included in the Consolidated Statement of Operations [Abstract]
Total stock-based compensation expense	997	285	1,358	663
General and administrative
Allocation of Stock-based Compensation Expense Included in the Consolidated Statement of Operations [Abstract]
Total stock-based compensation expense	$ 1,725	$ 489	$ 2,120	$ 1,051

STOCK-BASED COMPENSATION - Su58

STOCK-BASED COMPENSATION - Summary of Stock-Based Compensation Associated with Each Type of Award (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 4,288	$ 1,621	$ 5,860	$ 3,550
Stock options and RSUs and PSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	3,975	1,291	5,293	2,890
Employee stock purchase plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total stock-based compensation expense	$ 313	$ 330	$ 567	$ 660

STOCK-BASED COMPENSATION - Su59

STOCK-BASED COMPENSATION - Summary of the Weighted-Average Grant Date Fair Value of Options Granted (Details) - Stock options - $ / shares	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
The fair value of each option granted during the periods
Weighted average grant date fair value (in usd per share)	$ 3.51	$ 0.71	$ 2.74	$ 0.71
Expected term (in years)	3 years 9 months 18 days	4 years 7 months 6 days	4 years	4 years 7 months 6 days
Expected volatility	89.70%	84.90%	88.10%	85.00%
Annual risk-free rate of return	2.70%	1.80%	2.60%	1.80%
Dividend yield	0.00%	0.00%	0.00%	0.00%

NET LOSS PER SHARE - Schedule o

NET LOSS PER SHARE - Schedule of Computation of Basic and Diluted Net Loss Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Numerator:
Net loss	$ (3,738)	$ (12,093)	$ (8,866)	$ (35,398)
Denominator:
Weighted average common shares outstanding (in shares)	97,321	84,434	94,026	80,542
Net loss per share, basic and diluted (in usd per share)	$ (0.04)	$ (0.14)	$ (0.09)	$ (0.44)

NET LOSS PER SHARE - Schedule61

NET LOSS PER SHARE - Schedule of Potentially Dilutive Securities Excluded from the Computation of Diluted Net Loss Per Share (Details) - shares shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total (in shares)	13,812	11,305	12,949	10,482
Employee stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total (in shares)	8,102	8,068	8,259	8,262
RSUs and PSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total (in shares)	5,710	2,017	4,690	1,276
Warrants to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Total (in shares)	0	1,220	0	944